Hyundai accent 2015 1.6 fluid manual. Brand new clutch and Master slave cylinder installed. The clutch has also been bled a couple of days ago however the issue still persists. When driving the vehicle for more that 30 to 40 minutes the clutch starts releasing slower and slower until it starts slipping totally and cannot find any gear.This also occurs in heavy traffic as well. One then has to push the vehicle over to the side then wait an hour or two then you are able to maybe find a few gears until it occurs again. Once the vehicle has been parked overnight then clutch feels normal again until the issue randomly occurs again. What could this be? Multiple mechanics are not able to help and have spent quite abit already on the vehicle. Any help will be much appreciated

 

Suppose we start here,
When the clutch pedal is depressed, that creates pressure in the clutch Master cylinder that gets transferred on down to the clutch slave cyl. When adjusted correctly, that pressure at the slave cyl causes the clutch to release and separates the clutch disc from the flywheel on the engine. When the clutch slips, that means there is insufficient pressure from the clutch pressure plate assy against the disc allowing it to slip or not transfer power to the trans. If there is hydraulic pressure being applied to the slave cyl , that will pull the pressure from the assy allowing the disc to retreat an stop transferring mechanical power to the trans.
There are 2 conflicting things described here.
If something is allowing the clutch to release (slip) you should be able to shift gears.
Anyway, pressure may be building up in the hydraulic system, (Trapped air getting warm and expanding thereby increasing pressure to the slave cyl).

System could very well have trapped air and needs to be completely bled out. Clutch pedal free play should be about 1 inch. That is the amount of travel when depressing the clutch pedal before any resistance should be felt. Is that free ply there?

 

What you are saying makes lots of sense as it happens randomly usually in traffic (may be heating) so using the clutch in 1st and 2nd and also after a long road drive for about 30min and after stopping at a shop when you start the vehicle you can feel the clutch tension and slower release of the clutch. Hyundai did perform a bleeding of the system and hoped it would fix the issue however same thing kept occuring. The clutch keeps releasing slower and slower until the clutch is totally slipping unable to get any gear. Leaving it to "cool" overnight and clutch works perfectly next day until it randomly occurs again. With regards to the play of 1inch, yes there is that play when driving the car for example first thing in the morning but as you drive for a while the pedal tension changes begins to release slower. Small background the issue started occuring a few months after a service at Hyundai when no mechanical parts had been replaced. Prior to that the car was standing due to covid protocols. New clutch new slave was put in afterwards based on Hyundai recommendations and the system was bled on Friday and the same issue is happening. I don't think the issue can be a mechanical fault as the clutch drive like a gem first thing in the morning for example. Really don't have the cash for a gearbox removal again when they havent found and leaks and the current parts are all new. Thanks for the reply much appreciated

 

I don't know much about vehicles but been trying to find similar situations online. What seems to line up with my issue seems to be overheating of the fluid in the clutch or the master not releasing fluid back into the reservoir. From what I can recall this issue I'm having has only ever occured in hot weather with heavy traffic. Air or fluid heating up seems closest to the issue.

 

This is going to require some isolation checks. There could be a problem with the clutch master cyl vent possibly being clogged.. If that is the case, when the fluid becomes heated, it naturally expands and the vent allows the increased reservoir pressure to escape. If that master is defective , replacement may be required.

 

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Goch & Cooper Auto Services. These guys are Champions.They found the issue which was the Hydraulic pipe that was causing a build up of pressure, which in turn kept damaging both the master and slave cylinder. They found the issue by driving the vehicle until the issue occured which was at random times. Then stopped the vehicle when the issue started and began to work on the car wherever they broke down.

 

Could you be a little more specific as to what they had to do to correct the problem?

 

I am having the same problems. The clutch on my hyundai accent (2017) starts to get spongy and eventually gets stuck after driving for an hour usually when i am stuck in traffic and frequently changes to lower gears. After turning off the engine I can’t immediately restart since I can’t depress the clutch. But after a few minutes the clutch returns to normal and I could use it normally again. This happened to me twice already. Brought it to a mechanic but he told me he can’t fix issue and that I need a whole new clutch assembly. Can you elaborate on how your issue was fixed? Thanks!

 

It seems anytime when a shop /person doesn't understand how a hydraulic clutch works , they want to replace everything.

Grant you, there are a lot of defective (new) parts out there, anytime any master cyl is replaced , it MUST be bench bled to remove any trapped air and until this is done there will always be problems. Sometimes, the mechanical linkage doesn't allow for ports to be opened and air to escape. All these things need to be understood in order to do an effective diagnosis. The system is not complicated, but parts replacers have a difficult time with them.